1. Field of the Invention
The present invention relates to the use of strongly acidic cation exchange resins to reduce polyol catalyst concentrations to less than 1 part per million.
2. Description of the Related Art
Cuscurida et al, U.S. Pat. No. 4,535,189 disclose filter cakes formed by the filtering of a alkylene oxide polymer during the refining of the alkylene oxide polymer which contains a minor amount of alkylene oxide polymer which can be recovered therefrom by treating the filter cake with a lower aliphatic alcohol or an aqueous solution of aliphatic alcohol. It is preferred that methanol be the lower aliphatic alcohol. Cuscurida relates to an improved purification process wherein a filtration step is utilized as part of the purification sequence. It has been discovered in accordance with Cuscurida that in a process of this nature, the polyol that is occluded in the filter cake formed by the filtration step may be separately recovered therefrom by treating the filter cake with a lower aliphatic alcohol or an aqueous solution of such lower aliphatic alcohol. The alkylene oxide polymer has an average molecular weight of about 500 to 10,000 and can be recovered from the filter cake with an aqueous solution.
Louvar et al, U.S. Pat. No. 3,715,402 disclose a method for the removal of water insoluble impurities from water insoluble polyethers. The process comprises providing a mixture of water, polyether, a solvent in which the polyether is soluble, and an acid. The solvent has a density which is different than water and which is inert with respect to the polyether in water and is substantially immiscible in water. The acid is used in an amount sufficient to adjust the pH of the mixture to a pH of about 8 and when this is done, the polyether solvent is then separated from the water by a method such as electrostatic coallescence or subjugation centrifugal force. A stream of water containing dissolved water soluble impurities and a stream polyether solvent solution are separately recovered after the separation followed by separating the solvent from the polyether solvent solution.
Louvar et al, U.S. Pat. No. 4,137,396 disclose improvements in the process for the removal of residual catalysts from polyether polyols by use of a solvent wash and recovery system. Specifically, Louvar et al do disclose ion exchange techniques for the removal of catalysts but teach that such is not a satisfactory method for the removal of catalysts residue from polyols. Rather, Louvar et al disclose the use of adsorbents, such as "MAGNESOL" sold by Reagent Chemicals, which are employed in an aqueous mixture of water and crude polyol at temperatures ranging from 30.degree.-120.degree. C. The resulting mixture is spray washed and then cycled through a filter until sufficient filter cake is deposited on the filter and a catalyst refiltrate containing the polyol is obtained.
Kablitz et al, U.S. Pat. No. 4,476,297 disclose a process for the removal of catalyst residues from polyolefins which contain titanium and light metal halides and aluminum compounds. These impurities can be reduced by treating the polyolefin with a higher, preferably branched, aliphatic monocarboxylic acid having 6 to 10 carbon atoms. The present invention is not directed to purification of polyolefins and does not utilize aliphatic monocarboxylic acids.
Louvar et al, U.S. Pat. No. 3,823,145 disclose a process for purifying polyoxyalkylene ether polyols containing water soluble residual catalysts which comprises providing a mixture of water, polyol and solvent together with the polyol forms a water immiscible solution. The solution is subjected to centrifugal separation whereby the polyol solvent solution is separated from the water layer and the purified polyol is recovered from the polyol solvent solution by stripping off the solvent.
The present invention relates to the use of strongly acidic cation exchange/resins to reduce the polyol catalyst in the polyoxyalkylene polyol to a concentration of less than about 1 ppm. None of the art, alone or in combination, insofar as is known, discloses the process of the present invention.